Method and apparatus for making clear ice

ABSTRACT

A clear ice maker has a stationary open-top tray for containing a predetermined quantity of water. A grid has a plurality of open-bottom, open-top ice mold cavities and flexible filler means between the cavities to displace substantially all of the water into the cavities when the grid is in the tray. The side and bottom walls of the tray are heated to keep the water adjacent thereto from freezing. Air at below-freezing temperatures is directed over the open top of the tray and grid to freeze water into clear ice starting at the interface between the air and the water in the cavities and continuing downwardly toward the bottom wall of the tray. Harvesting mechanism periodically removes the grid and clear ice from the tray before the air has frozen the water in the cavities to the bottom wall of the tray; and then twists the grid to release the clear ice into a storage bucket.

11 1 3,775,992 51 Dec.4, 1973 METHOD AND APPARATUS FOR MAKING CLEAR ICE [75] Inventor: James A. Bright, Dayton, Ohio [73] Assignee: General Motors Corporation,

I Detroit, Mich.

22 Filed:' July 17,1972

[21] App]. No.: 272,410

Primary Examiner william E. Wayner Assistant Examiner.William E. Tapolcai, Jr. AttorneyWilliam S. Pettigrew et al.

[57'] ABSTRACT A clear ice maker has a stationaryopen-top tray for containing a predetermined quantity of water. A grid has a pluralityof open-bottom, open-top ice mold cavities and flexible filler means between the cavities to displace substantially all of the water into the cavities when the grid is in the tray. The side and bottom walls of the tray are heated to keep the water adjacent thereto from freezing. Air at below-freeging temperatures is directed over the open top of the tray and grid to freeze water into clear ice starting at the interface between the air and the water in the cavities and con tinuing downwardly toward the bottom wall of the tray. Harvesting mechanism periodically removes the grid and clear ice from the tray. before the air has frozen the water in the cavities to the bottom wall of the tray; and then twists the grid to release the clear ice into a storage bucket.

14 Claims, 16 Drawing Figures PATENTED DEC 75 SHEET 2 0F 6 METHOD AND APPARATUS FOR MAKING CLEAR ICE This invention relates to a method, and apparatus for making clear ice and, more particularly, to such apparatus for domestic refrigerators. n Clear ice has been a desire of users and a goal of manufacturers for years. Apparatus for making clear ice, however, has been cumbersome and suited only to commercial manufacture of ice. Heretofore, no one has simplified clear ice makers to the point where they are suitable in size, cost and operation to the relatively small confines of the freezer in a domestic refrigerator.

Accordingly, it is an object of this invention to make clear ice in a manner similar to that by which skim ice is formed on the surface of a puddle or pool by belowfreezing air in winter.

It is also an object of this invention to provide a clear ice maker wherein clear ice is formed on a removable,

poor heat-conducting support downwardly from an exposed surface on a bodyof water whereby to force gas and minerals entrained in said body of water ahead of the clear ice and into a remaining non-frozen portion of the body of water.

Another object of this invention is a method of making clear ice along an interface between below-freezing -air and a body of purified water in a freezer.

Another object of this invention is a method of making clear ice by conversion along an interface between below-freezing air and a body of purified water in a freezer.

A specific object is the provision of a method and apparatus for making clear ice in a container in the top portion of the water starting at the interface between the water and freezer air and continuing to freeze water downwardly toward the bottom of the tray, and periodically removing the frozen clear ice portion before it extends sufficiently toward the bottom of the tray to entrap gas and minerals in the water.

A more specific object is the provision of jamethod and apparatus for making clear ice in a container in a domestic refrigerator and storing said clear ice in a receptacle in a freezer comprising containing water in a tray, heating the bottom of the tray to keep the lower portion of the water in a liquid state, freezing the top portion of the water by distributing a flow of belowfreezing air thereover starting at the interface between the water and the below-freezing air and continuing to freeze water downwardly toward the bottom of the tray, periodically removing the frozen clear ice portion before it extends sufficiently toward the bottom of the tray to entrap gas and minerals in the water, and moving the clear ice portion during its periodic removal through said below-freezing air slow enough to dry said clear ice portion before it is stored so that it will not stick to other clear ice portions in said receptacle during storage thereof.

Another object of this invention is the provision in the clear ice making apparatus of the last object for forming the clear ice in block-like cubes.

Another object of this invention is the provision in the clear ice maker of the foregoing objects of a Warpable grid in a water-containing tray, the inside of said grid having cube forming cavities of inverted truncated pyramidal shape and the outside of said grid between said cavities being filled with an anti-stick material to displace substantially all of the water from the tray into the cavities and provide easy removal of the grid and clear ice from the tray, said, anti-stick material also being flexible to distribute forces uniformly throughout said grid when the grid is removedfrom the tray and warped to harvest the clear ice.

A still further object of this invention is a clear ice maker in a freezer comprising a tray containing a body of water and fan means distributing sub-freezing air over the top surface of said body of water whereby to initiate the freezing of clear ice along the interface between said air and said top surface, heating means to maintain said body of water in a liquid state adjacent said tray below said clear ice, and control means to de' energize said heating means when said fan is not blowing sub-freezing air over the top surface of said body of water, thereby to reduce heat dissipated in said freezer.

A still further object of this invention is a clear ice maker in a freezer comprising a tray containing a body of water, a grid in said tray displacing said body of water into cavities in said grid, fan means distributing sub-freezing air over the top surface of said body of water in said grid whereby to initiate the freezing of clear ice along the interface between said air and said top surface, and a bucket for storing said clear ice, heating means to maintain said body of water in a liquid state adjacent said tray below said clear ice, harvesting mechanism for removing said grid from said tray and depositingsaid clear ice in said bucket, said heating means comprising a first heater for the sidewall of the tray. and a second heater for the bottom wall of the tray, and control means. providing for continuous energization of said first heater andenergiization of said second heater only when said bucket is full of clear ice or not in said freezer.

It is also an object of this invention to provide in the clear ice maker of any of the foregoing objects a tray and grid combination containing a, body of water having an exposed top planar surface area of substantially 65 square inches in a freezing ambient 0 F.) for initial freezing as clear ice and a timer for initiating the removal of said grid from said tray and the harvesting of said clear ice substantially every two and one-half hours.

Another object in the clear ice maker of this invention is the provision of common liquid level seeking fill means including a tray inside the freezer and a floatcontrolled reservoir outside the freezer in liquid-flow communication through a tube connected to the bottom wall of said tray.

A further object in the clear ice maker of this invention is the provision of a stationary, container comprising a tray adapted to, containon the inside thereof a body of water with a relatively large top surfacearea exposed to a freezing ambient (0 F.) for initial freezing as clear ice, insulation surrounding the side and bottom walls of said tray on the outside thereof and heaters sandwiched between the insulation and the tray for exposing the body of water below said clear ice to, an above-freezing ambient (36 F.).

Another object is the provision in the clear ice maker of this invention of a stationary container comprising an insulated and heated tray adapted to contain a body of water with a relatively large area top surface portion exposed in the freezer of a domestic refrigeratonfan means adapted to distribute air to said top surface co- 3 extensively with said top surface at a quantity of substantially 10 to 15 cubic feet per minute and at a temperature of substantially minus 10 F. to minus 12 F. to freeze the top surface portion only into clear ice, and harvesting mechanism for moving said clear ice from said tray through said air at a rate sufficient to dry said clear ice before it is stored.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

IN THE DRAWINGS FIG. 1 is a fragmentary section through the freezer compartment of a domestic refrigerator showing in side elevation the automatic clear ice maker of this invention;

FIG. 2 is a front elevational view taken along line 22 in FIG. 1 with parts broken away to provide a schematic representation of the clear ice harvesting cy cle;

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a fragmentary sectional view taken along line 4-4 in FIG. 3 and showing a portion of the water fill system;

FIG. 5 is a sectional view taken along line 55 in FIG. 3 and showing an insulated and heated water containing tray;

FIG. 6 is a fragmentary sectional view taken along line 66 in FIG. 4;

FIG. 7 is a perspective view of a side by side refrigerator freezer showing the clear ice maker of this invention installed in a portion of the freezer compartment;

FIG. 8 is a perspective view of the clear ice maker of this invention in an ice harvesting mode;

FIG. 9 is a sectional view with parts broken away taken along line 99 in FIG. 3 to show the ice harvesting mechanism and weight sensing means;

FIG. 10 is a side elevational view'with parts broken away taken along line 10l0 in FIG. 9;

FIG. 11 is a sectional view of the ice harvesting mechanism taken along line 11-11 in FIG. 10 to show the ice making cycle timer and drive mechanism;

FIG. 12 is a perspective view from the front side with parts broken away to show ice harvesting mechanism for moving the ice grid and weight sensing means for sensing, first, the presence of an empty ice storage bucket and, secondly, a predetermined load of ice in the bucket;

FIG. 13 is a perspective view of the ice harvesting mechanism from the back side to show the ice making cycle timer and drive mechanism;

FIG. 14 is a sectional view of a water fill system suitable for use with this invention;

FIG. 15 is a pictorial representation of the elec-trical control system of this invention; and

FIG. 16 is a schematic wiring diagram.

GENERAL In accordance with the teachings of this invention and with particular reference to FIG. 7, a domestic refrigerator 20 is shown. The refrigerator is of the side by side type wherein a right side portion encloses a refrigerated food compartment 22 and the left side portion encloses a lower freezer portion 24 for storing frozen foods and an upper freezer portion 26 enclosing the clear ice maker of this invention shown generally at 28. A vertical full length door 30 may be used to close both the upper and lower freezer compartments 24, 26.

In general, the clear ice maker 28 (FIGS. 1 and 8) includes a tray and heater assembly 34, an ice cube grid 36, an ice storage bucket assembly 38, a weight sensing means 39 for bucket and ice, an ice harvesting mechanism 40, and a water fill system 42.

TRAY AND HEATER ASSEMBLY The tray and heater assembly 34 (FIGS. 4 and 5) is supported by bracket means 46 from a sidewall 48 of the freezer compartment 26. The assembly includes a drawn sheet metal housing 50 forming on one side thereof a water containing tray 52 having a sidewall 54 and a bottom wall 56 and on the other side thereof a cavity filled with freon-filled urethane foam insulation 58. A pair of heaters 60, 62 surround the tray 52. Heater 60 is adapted for heating all four sidewalls 54 of the tray and thereby normally exposes the bottom side of the tray (beneath the ice) to above-freezing temperature. This retains that portion of water along the bottom side of the tray in a liquid state. For this purpose, heater 60 is comprised of 90.8 inches of vinyl covered resistance wire rated at 115 volts, 6.5 7.5 watts, 250 ohms per foot reference.

Heater 62 is adapted for supplying additional heat to the tray bottom wall 56 under certain circumstances to keep ice from freezing all the way down to the bottom wall, and is comprised of 41.7 inches of vinyl covered resistance wire rated at l 15 volts, 2.8 3.2 watts, 1,268 ohms per foot reference.

. Heater 60 is sandwiched between a sheet 66 of 0.005 aluminum foil and a sheet 68 of 0.002 aluminum foil. Similarly, bottom wall heater 62 is sandwiched between a sheet 70 of 0.005 aluminum foil and a sheet 72 of 0.002 aluminum foil. The mating edges of foilsheets 66 and 68 are heat-sealed as are the mating edges of foil sheets 70 and 72. Both heater assemblies 60 and 62 are foamed in place between the tray and the urethane foam.

Also foamed in place is a tray fill tube 76 of polypropylene in heat transfer relation to heater 62 to prevent freeze-up and adapted to supply water to fill tray 52 through the bottom wall 56 of the tray. Electrical leads may enter the freezer through tubing 77.

WATER FILL SYSTEM The water fill system 42 will now be described with reference to FIGS. 1 and 4. In general, water is supplied to tray 52 from a reservoir 78 defined by a water valve housing 80 attached to the back wall 82 of the refrigerator 20 behind the freezer compartment 26. Water in reservoir 78 communicates with tray 52 through outlet 84 in the reservoir housing and tubing or conduit means 86 connecting outlet 84 with tray fill tube 76 through a protector tube base 90 (FIG. 4). Water contained in tray 52 seeks a common level with water in reservoir 78. Thus, the desired fill level in the tray is achieved by predetermining the water level in reservoir To control the level of water in reservoir 78, water valve housing 80 includes a float 94 pivotally attached at 96 to a wing hinge bracket 98. Top wall 100 of housing 80 carries a water valve assembly 102 including a water inlet 104 and a water outlet 106. A domestic supply'of purified water may be connected to the inlet 104. Valve 'pin 108 (slidably supported on three ribs 109) has a rubber valve portion 110 adapted for closing against a valve seat 112. At the lower end of assembly 102, a valve pin actuator 114 pivots about axis 116 in response to the upward force of float 94 at one end 120 as balanced against a water level adjustment mechanism122 at the other end 124. Water level may be adjusted by a remote knob 125 turning worm gears 126, 128 against spring 130.

The water level is adjusted at 125 in a manner to shut off the water supply at 110, 112 when the water level A (FIGS. 2 and 14) exists in both reservoir 78 and tray 52. In general, a fresh charge of water is supplied to tray 52 during an ice harvesting cycle when grid 36 is out of the tray. It should be noted that water level A will be raised to water level B when the grid is in the tray. The grid is constructed in a manner to displace substantially all water from the tray into the grid cavities for making clear ice. In this way, the water so displaced is available to form cubes in the grid cavities and, accordingly, does not form an adhesive film of ice between the grid and tray which resists the separation of grid and tray at the start of an ice harvesting cycle.

ICE CUBE GRID Ice cube grid 36 (FIGS. 2, 3 and 8) has characteristics of poor heat conduction and good flexibility at low temperature with good ice release and return memory. It is comprised of a polypropylene housing 140 defining cavities 142 for a plurality of ice cubes. Each cavity 142 has an inverted truncated pyramidal shape. On the outside of the housing between the cavity forming portions thereof, a flexible filler 146 of RTV silicone rubber fills the space between the cube forming cavities on the outside of grid 36. The filler material should have an anti-stickcharacteristic to aid in the release of the grid from the tray during ice harvesting. It should be sufficiently flexible to distribute forces throughout the grid when the grid is warped for harvesting cubes. Aside from these characteristics, the filler 146 serves to force water in the tray upwardly intothe cube forming cavities'of the grid. Thus, with the grid in place in the tray (FIG. 2, solid line), water level A will become water level B.

ICE STORAGE BUCKET ASSEMBLY The ice storage bucket assembly 38 will be described with reference to FIGS. 1 and 2. An ice container 150 of high impact polystyrene rests on a steel wire shelf 152. The shelf pivots about a support foot 154 on the bottom wall 156 of freezer portion 26 and includes an upright bracket 158 at the rear thereof which hangs from a weight sensing means 39 in a manner to keep WEIGHT SENSING MEANS The weight sensing means 39 (FIGS. 9 and is comprised of a nylon weigh shaft 176 having a hooked portion 178 for gripping a loop in the upright shelf bracket 158. The weigh shaft is connected to a stainless steel container weigh bar 188 which pivots about 198 and is electrically connected to terminal 190 by resting thereon. An ice weigh bar 192, also stainless steel, is disposed above the container weigh bar and pivots about a brass pin 194. The other end of ice weigh bar 192 normally rests in electrically conducting relation- I ship against a brass weigh bar stop and terminal 196.

The container weigh bar includes a terminal 198 which cooperates with terminal 196 to comprise a weigh switch. Another terminal 200 is disposed above the ice weigh bar 192 and is normally out of electrical contact with the weigh bar. In brief, the presence of container on shelf 152 will cause the weigh shaft 176 to pull down in a manner to cause container weigh bar 199 to touch ice weigh bar 192 and complete a circuit between terrninals 198 and 196. When container 250 fills up with apredetermined full loadof ice cubes, the further downward movement of weigh shaft 176 will cause container weigh bar 188 to force ice weigh bar 192 out of electrical contact with terminal 196 and into electrical contact with terminal 200. For additional details of the weight sensing mechanism suitable for use with this ice maker, reference may be had to my copending' application Ser. No. 302,743, filed Nov. 1, 1972. Y

HARVESTING MECHANISM The harvesting mechanism 40 will now be described with reference to FIGS. 9, 10, 11, 12 and 13.. With particular reference to FIGS. 12 and 13, the harvesting mechanism is comprised of a box-like plastic casing 210 defining a compartment 212 for the grid pivoting and twisting gears on one side of a gear mounting plate 214. on the other side of the mounting plate 214, the housing is divided into a drive compartment 216 and a timer compartment 218. I

The means for pivoting or removing and twisting or warping grid 36are disposed in gear compartment 212. A cam and crank gear 220 is rotatably mounted on plate 214 and is rotatably driven from the other side of the plate by a pair of worm gears 222, 224 which are, in turn, driven by drive motor assembly 226. The cam and crank gear 220 is comprised of a cam portion 230 and a gear portion 232. The cam 230 cooperates with a holding switch 234 through a switch-actuator 236 so that the holding switch is closed when the switch actuator 236 rides the outer periphery of the cam. In the position of FIG. 12, switch actuator 236 is disposed in a notched portion of the cam periphery to open switch 234. Gear 232 directly drives a timer gear 240and includes a crank portion 242 in a slot 244 of segment gear 246. Thus, one rotation of crank andcam gear 220 will cause the segment gear 246 to rock back and forth about its pivot point 250.

The segment gear is drivably connected to grid drive gear 252 which extends outside the mechanism casing 210 where a D socket 254 is adapted for connection with a similarly shaped stud on grid 36 as at 256 (FIG. 3).

Timer gear 240 is pivotally mounted on mounting plate 214 and extends therethrough for directly driving ball timer 260. In general, and with reference to FIG. 11, ball timer 260 is comprised! of a pivotable timer switch arm 262 including a magnetic slug 264 disposed adjacent the normally non-magnetic periphery 266 of a circular housing 268. The housing includes a diametrical void 270 filled with a viscous fluid. Within the slug 264 where its presence will attract the slug magnetically and close a timer switch 280 (FIG. 16) between terminals 282 and 284 (FIG. 15). For additional details of the ball timer, reference may be had to my copending application Ser..No. 302,875, filed Nov. 1,

7 2' WOFERATION An ice making cycle in accordance with the teachings of this invention will now be described. Water level in reservoir 78 is adjusted by means of water level adjustment 125 to provide a predetermined water level A when grid 36 is not in tray 52. Once the adjustment is made, water valve 110, 112 will be opened and closed by the action of float 94 and lever 1 14 to rapidly return to this water level during the time that grid 36 is being rotated out of tray 52 during an ice harvesting cycle.

With grid 36 in tray 52, substantially all of the water comprising water level A will be forced through the open bottom of each grid cavity 142 to form a water level B near the top of the grid cavities. This water level B will provide in the embodiment shown a water depth of approximately 1 inch in the tray. Fan means 285 (FIG. 16) blows air through and includes a duct 290 on the back wall of the freezer compartment 26 which distributes a quantity to 15 cubic feet per minute) of below-freezing air (minus 10 F. to minus 12 F.) uniformly over the exposed top planar surface (water level B) of the water in the grid cavities. The air is cooled by refrigerating or cooling means including a compressor 286 and a temperature responsive cold control 289 for controlling fan means 285 and compressor 286. The refrigerating means may include a defrost arrangement including a defrost heater 287 and limiter switch 288 in series with a defrost timer contact 299. Additional distribution may be accomplished by suitable means such as adjustable louvers 292 at the duct 290.

A skim of clear ice (FIG. 3) starts to form at water levelB along the top planar surface of water filling each cube cavity 142. Ice thickens from this top surface progressively downwardly. During the generation of this ice, heater 60 is energized to heat the body of water in each tube cavity below the ice forming along the top surface of the body of water in each cube cavity. During the time that ice is progressively freezing from the top surface of each cube cavity toward the bottom wall 56 of tray 52, ball 272 in timer 260 is falling toward magnetic slug 264. When the slug is attracted to the ball, timer switch 280 closes (FIG. 16). This occurs when the clear ice is in the form of a cube 296 approximately one-half inch thick. With the ice maker in a 0 F. freezer and the refrigerator in a 70 F. room ambient, compressor 286 in the freezing system normally operates 60 70 percent of the time. These parameters provide for freezing clear ice one-half inch thick in about two and one-half hours. Thus, timer 260 is designed so that the ball 272 will taken two and one-half hours to close timer switch 280. The saturation of the body of water with gas and minerals is a factor in determining this freezing rate. In general, the more saturated the water is, the slower the freezing rate should be for clear ice.

Assuming ice container is in place on shelf 152 and timer switch 280 closes, a circuit will be completed between terminal 198 and terminal 196 and motor 226 will be energized. In response to the operation of motor 226 through worm gears 222, 224, cam and crank gear 220 will start to rotate. The first function occurs when cam 230 through switch actuator 236 closes holding switch 234. The holding switch assures completion of a harvesting cycle by forming a shunt circuit around timer switch 280. This is necessitated by the opening of switch 280 as timer housing 268 starts to rotate and moves ball 272 away from magnetic slug 264.

With reference to FIGS. 2 and 3, grid 36 starts to rotate with substantially one-half inch cubes 296 of clear ice in the top portion only of each cavity 142. Unfrozen water 298 beneath the cubes remains in tray 52 in a liquid state. Tray housing 50 includes an upstanding flange 300 joumalling a stud 302 projecting from one corner of the grid. A stud at the same corner on the opposite end of the grid (not shown) tits in the D socket 254 of grid drive gear 252. As grid 36 rotates from the installed position X (FIG. 2) through the upright position Y to the harvesting position Z, the grid will engage a raised boss 304 which halts the pivoting motion of the grid at its outer end. However, the harvesting mechanism continues to drive the grid causing the end nearest the driving mechanism to continue rotation to warp the grid in a manner to release clear ice cubes 296 from the grid. The released cubes fall into the ice container 38 therebelow.

The time it takes to move the grid from position X to position Z is predetermined as approximately 5 minutes. During this time the exposed surface of each clear ice cube 296 in the grid is exposed to the cold dry air in the 0 F, freezer. This air in this amount of time dries the cube surface before the cube is released from the grid and stored in the container. Since the cubes are dry when stored, they tend not to stick together.

After the cubes are harvested, the continued rotation of crank 232 operating through its crank 242 in the slot of segment gear 246 will return the grid to its installed position X.

When the container 150 is full of ice, this added weight will, through the weight sensing means 39, close a circuit between terminal 198 and terminal 200 to energize the tray bottom heater 62. This added heat will prevent ice forming in the grid from freezing all the way to the bottom of the tray.

It is also desirable to reduce heat dissipated in the freezer by deenergizing the tray side and bottom heater 60 when sub-freezing air is unavailable in the freezer. For this purpose (FIG. 16), heater 60 is placed in parallel with fan means 285 and compressor 286 so that it will be deenergized when cold control 289 is satisfied and the circuit opened.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is:

l. A clear ice maker comprising tray means adapted to contain a body of water and having an open top, a grid in said tray means for supporting clear ice to be formed thereon and having a poor heat conducting characteristic, said tray means adapted to provide the lower portion of said body of water with an abovefreezing temperature to maintain it in a liquid state, refrigerating means adapted to expose the surface of said body of water at saidopen top to below-freezing ambient air for a sufficient period to start the freezing of a surface layer of ice on said body of water and to continue the freezing thereof progressively downwardly in supporting engagement with said grid, and means adapted to remove said grid and the ice supported by said grid from said tray means before said ice extends to the bottom of said tray means.

2. A clear ice maker comprising tray means adapted to contain a volume of water in a refrigerated ambient, a grid in said tray means for supporting clear ice to be formed thereon and i having a poor heat conducting characteristic, said grid on the inside thereof having a cube forming cavity defining the top surface of said volume of water with'said refrigerated ambient, heating means adapted to provide the lower portion of said volume of water with an above-freezing temperature to maintain it in a liquid state, refrigerating means adapted to expose said volume of water to belowfreezing ambient air along said top surface for a sufficient period to start freezing a surface layer of ice on said volume of water in said cube forming cavity and to continue the freezing thereof progressively downwardly in supporting engagement with said grid, means adapted to periodically automatically remove said grid and the ice supported by said grid from said tray means before said ice extends to the bottom of said tray means, and means connected to the bottom of said tray means for supplying make-up water to said tray means during the periodic removal of said ice to restore said volume of water to thevolume contained in said tray means before the freezing of said surface layer of ice was started. 7

3. A method of making clear ice adjacent a support comprising containing a body of water adjacent said support, heating the lower portion of said body of water to aboveafreezing temperature-whereby to retain said lower portion in a liquid state, distributing a flow of air at below-freezing temperature uniformly over the top surface of said body of water for a sufficient period to start the freezing of a surface layer of ice on said body of water and to continue the freezing thereof progressively downwardly in supporting relationship with said support, and periodically removing said support and the ice supported thereby before the ice extends to the bottom of said body of water whereby to avoid the entrapment of gas and minerals entrained in said body of water.

4. A method of making clear ice on a support having a poor heat conducting characteristic and storing said air at a rate sufficient to dry said ice before it is stored in said receptacle. i

5. A clear ice maker comprising a grid in a tray adapted to contain water, means for exposing the bottom side of said tray to above-freezing temperatures whereby to retain a lower portion of water in said tray in a liquid state,'means exposing the top surface of water in said tray to below-freezing temperatures for a sufficient period to start the freezing of 'a portion of said water from said top surface down into clear ice, said grid on the inside thereof having a cube forming cavity defining the top surface of said water and on the outside thereof a void formed by said cavity, said void clear ice in a receptacle in a freezer comprising containing a body of water adjacent said support, heating the lower portion of said body of water to abovefreezing temperature whereby to retain said lower portion in a liquid state, distributing a flow of air at belowfreezing temperature uniformly over the top surface of said body of water for a sufficient period to start the freezing of a surface layer of ice on said body of water and to continue the freezing thereof progressively downwardly in supporting engagement with said support, periodically removing the support and the ice supported thereon before the ice extends to the bottom of said body of water whereby to avoid the entrapment of gas and minerals entrained in said body of water, and moving said support and the ice supported thereon during the periodieremoval thereof through said flow of filled sufficiently with filler material to displace substantially all of the water from the tray into the cavity, said filler material having an anti-stick characteristic with respect to ice and saidtray to provide easy removal of the grid and clear ice from the tray, means for periodically removing the grid and clear ice from said tray before the clear ice extends a sufficient distance toward the bottom side of said tray to entrap gas and minerals which may be entrained in said water, and means for releasing said clear ice from said grid.

6. A clear ice maker comprising a warpable grid in a tray adapted to contain water, heating means for heating the bottom side of said tray to above-freezing temperatures to retain a lower portion of water in said tray in a liquid state throughout the clear ice making process, fan means distributing sub-freezing air over a top planar surface of water in said tray for a sufficient period to initiate the freezing of clear ice along the interface between said air and said top planar surface and to continue the freezing of clear ice downwardly in said grid, said grid on the inside thereof having cube forming cavities of inverted truncated pyramidal shape defining in an upper portion of said cavities the top surface of water in said tray and on the outside thereof voids formed by said cavities, said voids filled sufiiciently with filler material to displace substantially all of any water in the tray from the tray into the cavities,

said filler material and said grid having an anti-stick characteristic with respect to ice and said tray to provide easy removal of the grid and clear ice cubes from the tray and the clear ice cubes from said grid, means for periodically removing the grid and clear ice cubes from said tray before the freezing of clear icedownwardlyreachessaid lowerportion of water in said tray and entraps in said cubes any gasand minerals which may be entrained in said lower portion of water, and means for warping said grid to release said clear ice cubes therefrom, said filler material having a characteristic of flexibility to distribute forces uniformly throughout said grid when the grid is removed from the tray and warped to release the clear ice cubes.

7. The clear ice maker of claim 6 wherein said grid is polypropylene and said filler material is RTV silicone rubber.

8. The clear ice maker of claim 6 wherein the top surface of water adapted for freezing as clear ice is at least i square inches, said fan means is distributing air hav- 9. In combination, a domestic freezer, a clear ice maker in said freezer comprising a warpable grid in a tray adapted to contain water, heating means energizable for heating the bottom side of said tray to abovefreezing temperatures to retain a lower portion of water in said tray in a liquid state throughout the clear ice making process, fan means operable for cooling said freezer to substantially F. and vfor distributing subfreezing air at substantially minus F. to minus 12 F. overta top planar surface of water in said tray for a sufficient period to initiate the freezing of clear ice along the interface between said air and said top planar surface and to continue the freezing of clear ice downwardly in said grid, said grid on the inside thereof having a cube forming cavity defining in an upper portion of said ,cavity the top surface of water in said tray and on the outside thereof a' void formed by said cavity, said void filled sufficiently with filler material to displace substantially all of any water in the tray from the tray into the cavity, and control means deenergizing said heating means when said fan means is not operating for distributing said sub-freezing air to reduce heat dissipated in said freezer.

10. A clear ice maker in a freezer comprising a tray having side and bottom walls adapted to contain a body of water, a grid in said tray having cavity-forming means for displacing the body of water contained by said walls into the cavity, fan means distributing subfreezing air over the top planar surface of said body of water in said grid cavity for a sufficient period to initiate the freezing of clear ice in said grid cavity along the interface between said air and said top planar surface and to continue the freezing of clear ice downwardly in said grid cavity, and a bucket for storing said clear ice in said freezer and being removable from said freezer, heating means energizable to maintain said body of water in a liquid state adjacent said tray below the freezing clear ice, harvesting mechanism for removing said grid and clear ice from said tray before the freezing of clear ice downwardly in said grid cavity reaches the bottom wall of said tray and depositing said clear ice in said bucket, said heating means comprising a first heater for the sidewall of the tray and a second heater for the bottom wall of the tray, and control means providing for continuous energization of said first heater and energization of said second heater only when said bucket is full of clear ice or removed from said freezer whereby to maintain said body of water below the freezing clear ice at substantially 36 F.

11. The clear ice maker of claim 10 wherein said first and second heaters are vinyl covered resistance wire retained in a foil sandwich between said side and bottom walls of the tray on the outside thereof and a layer of foam insulation.

12. In combination with an insulated cabinet wall defining a freezer compartment adapted to contain air at subfreezing temperatures, a clear ice maker in said freezer compartment, saidvclear ice maker comprising a tray on the inside of said insulated cabinet wall having side and bottom tray walls adapted to contain water therein at a predetermined level, cooling means supplying air at sub-freezing temperatures to the top surface of water contained in said tray at said predetermined level for a sufficient period to start freezing an upper portion of said water from said top surface downwardly into clear ice, heating means maintaining a bottom portion of said water in a liquid state adjacent said bottom tray wall, and water fill means for refilling said tray with water to said predetermined level when the upper clear ice portion is removed from said tray, said fill means including a reservoir adapted to contain water therein in a liquid state at said predetermined level and means for maintaining water in said reservoir at said predetermined level, said reservoir being on the outside of said insulated cabinet wall substantially in the same horizontal plane as said tray, and conduit means interconnecting said reservoir and said tray from connections with said reservoir and tray below said predetermined level to place said reservoir in liquid flow communication with the bottom portion of water in the tray whereby water is supplied from said reservoir to said tray through said conduit means until the water level in said tray and reservoir is common at said predetermined level.

13. The combination of claim 12 wherein the connection of said conduit means with said tray is in heat transfer relationship with 'said heating means whereby water in the conduit means on the inside of said insulated cabinet wall remains in a liquid state.

14. The combination of claim 12 wherein the heating means and the connection of said conduit means with said tray are foamed in place by insulation on the out side of said tray walls.

PO-ww UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO. 3,775,992 Dated DecemberA, 1973 Inventor(' x) James A Bright It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 28 "conversion" should read convection Column 3, line 57 "elec-trical" should read electrical Column 4, line 52 "Figures 1 and 4" should read Figures 1 and 14 flcolumn 6,

line 14, 199" should read l8 8 line 16, "250" 150 Column 7,

line 48, "tube" should read cube line 62, "taken" take Column 8, line 40' After "crank" (1st occurrence) insert gear Signed and sealed this 12th day of November 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

1. A clear ice maker comprising tray means adapted to contain a body of water and having an open top, a grid in said tray means for supporting clear ice to be formed thereon and having a poor heat conducting characteristic, said tray means adapted to provide the lower portion of said body of water with an abovefreezing temperature to maintain it in a liquid state, refrigerating means adapted to expose the surface of said body of water at said open top to below-freezing ambient air for a sufficient period to start the freezing of a surface layer of ice on said body of water and to continue the freezing thereof progressively downwardly in supporting engagement with said grid, and means adapted to remove said grid and the ice supported by said grid from said tray means before said ice extends to the bottom of said tray means.
 2. A clear ice maker comprising tray means adapted to contain a volume of water in a refrigerated ambient, a grid in said tray means for supporting clear ice to be formed thereon and having a poor heat conducting characteristic, said grid on the inside thereof having a cube forming cavity defining the top surface of said volume of water with said refrigerated ambient, heating means adapted to provide the lower portion of said volume of water with an above-freezing temperature to maintain it in a liquid state, refrigerating means adapted to expose said volume of water to below-freezing ambient air along said top surface for a sufficient period to start freezing a surface layer of ice on said volume of water in said cube forming cavity and to continue the freezing thereof progressively downwardly in supporting engagement with said grid, means adapted to periodically automatically remove said grid and the ice supported by said grid from said tray means before said ice extends to the bottom of said tray means, and means connected to the bottom of said tray means for supplying make-up water to said tray means during the periodic removal of said ice to restore said volume of water to the volume contained in said tray means before the freezing of said surface layer of ice was started.
 3. A method of making clear ice adjacent a support comprising containing a body of water adjacent said support, heating the lower portion of said body of water to above-freezing temperature whereby to retain said lower portion in a liquid state, distributing a flow of air at below-freezing temperature uniformly over the top surface of said body of water for a sufficient period to start the freezing of a surface layer of ice on said body of water and to continue the freezing thereof progressively downwardly in supporting relationship with said support, and periodically removing said support and the ice supported thereby before the ice extends to the bottom of said body of water whereby to avoid the entrapment of gas and minerals entrained in said body of water.
 4. A method of making clear ice on a support having a poor heat conducting characteristic and storing said clear ice in a receptacle in a freezer comprising containing a body of water adjacent said support, heating the lower portion of said body of water to above-freezing temperature whereby to retain said lower portion in a liquid state, distributing a flow of air at below-freezing temperature uniformly over the top surface of said body of water for a sufficient period to start the freezing of a surface layer of ice on said body of water and to continue the freezing thereof progressively downwardly in supporting engagement with said support, periodically removing the support and the ice supported thereon before the ice extends to the bottom of said body of water whereby to avoid the entrapment of gas and minerals entrained in said body of water, and moving said support and the ice suppoRted thereon during the periodic removal thereof through said flow of air at a rate sufficient to dry said ice before it is stored in said receptacle.
 5. A clear ice maker comprising a grid in a tray adapted to contain water, means for exposing the bottom side of said tray to above-freezing temperatures whereby to retain a lower portion of water in said tray in a liquid state, means exposing the top surface of water in said tray to below-freezing temperatures for a sufficient period to start the freezing of a portion of said water from said top surface down into clear ice, said grid on the inside thereof having a cube forming cavity defining the top surface of said water and on the outside thereof a void formed by said cavity, said void filled sufficiently with filler material to displace substantially all of the water from the tray into the cavity, said filler material having an anti-stick characteristic with respect to ice and said tray to provide easy removal of the grid and clear ice from the tray, means for periodically removing the grid and clear ice from said tray before the clear ice extends a sufficient distance toward the bottom side of said tray to entrap gas and minerals which may be entrained in said water, and means for releasing said clear ice from said grid.
 6. A clear ice maker comprising a warpable grid in a tray adapted to contain water, heating means for heating the bottom side of said tray to above-freezing temperatures to retain a lower portion of water in said tray in a liquid state throughout the clear ice making process, fan means distributing sub-freezing air over a top planar surface of water in said tray for a sufficient period to initiate the freezing of clear ice along the interface between said air and said top planar surface and to continue the freezing of clear ice downwardly in said grid, said grid on the inside thereof having cube forming cavities of inverted truncated pyramidal shape defining in an upper portion of said cavities the top surface of water in said tray and on the outside thereof voids formed by said cavities, said voids filled sufficiently with filler material to displace substantially all of any water in the tray from the tray into the cavities, said filler material and said grid having an anti-stick characteristic with respect to ice and said tray to provide easy removal of the grid and clear ice cubes from the tray and the clear ice cubes from said grid, means for periodically removing the grid and clear ice cubes from said tray before the freezing of clear ice downwardly reaches said lower portion of water in said tray and entraps in said cubes any gas and minerals which may be entrained in said lower portion of water, and means for warping said grid to release said clear ice cubes therefrom, said filler material having a characteristic of flexibility to distribute forces uniformly throughout said grid when the grid is removed from the tray and warped to release the clear ice cubes.
 7. The clear ice maker of claim 6 wherein said grid is polypropylene and said filler material is RTV silicone rubber.
 8. The clear ice maker of claim 6 wherein the top surface of water adapted for freezing as clear ice is at least 65 square inches, said fan means is distributing air having a sub-freezing temperature of substantially minus 10* F. to minus 12* F. at substantially 10 to 15 cubic feet per minute, and said removing means includes a timer controlling the removal of the grid and clear ice cubes from said tray substantially once every two and one-half hours.
 9. In combination, a domestic freezer, a clear ice maker in said freezer comprising a warpable grid in a tray adapted to contain water, heating means energizable for heating the bottom side of said tray to above-freezing temperatures to retain a lower portion of water in said tray in a liquid state throughout the clear ice making process, fan means operable for cooling said freezer to substantially 0* F. and for distributing sub-freezing air at substantially minus 10* F. to minus 12* F. over a top planar surface of water in said tray for a sufficient period to initiate the freezing of clear ice along the interface between said air and said top planar surface and to continue the freezing of clear ice downwardly in said grid, said grid on the inside thereof having a cube forming cavity defining in an upper portion of said cavity the top surface of water in said tray and on the outside thereof a void formed by said cavity, said void filled sufficiently with filler material to displace substantially all of any water in the tray from the tray into the cavity, and control means deenergizing said heating means when said fan means is not operating for distributing said sub-freezing air to reduce heat dissipated in said freezer.
 10. A clear ice maker in a freezer comprising a tray having side and bottom walls adapted to contain a body of water, a grid in said tray having cavity-forming means for displacing the body of water contained by said walls into the cavity, fan means distributing sub-freezing air over the top planar surface of said body of water in said grid cavity for a sufficient period to initiate the freezing of clear ice in said grid cavity along the interface between said air and said top planar surface and to continue the freezing of clear ice downwardly in said grid cavity, and a bucket for storing said clear ice in said freezer and being removable from said freezer, heating means energizable to maintain said body of water in a liquid state adjacent said tray below the freezing clear ice, harvesting mechanism for removing said grid and clear ice from said tray before the freezing of clear ice downwardly in said grid cavity reaches the bottom wall of said tray and depositing said clear ice in said bucket, said heating means comprising a first heater for the sidewall of the tray and a second heater for the bottom wall of the tray, and control means providing for continuous energization of said first heater and energization of said second heater only when said bucket is full of clear ice or removed from said freezer whereby to maintain said body of water below the freezing clear ice at substantially 36* F.
 11. The clear ice maker of claim 10 wherein said first and second heaters are vinyl covered resistance wire retained in a foil sandwich between said side and bottom walls of the tray on the outside thereof and a layer of foam insulation.
 12. In combination with an insulated cabinet wall defining a freezer compartment adapted to contain air at subfreezing temperatures, a clear ice maker in said freezer compartment, said clear ice maker comprising a tray on the inside of said insulated cabinet wall having side and bottom tray walls adapted to contain water therein at a predetermined level, cooling means supplying air at sub-freezing temperatures to the top surface of water contained in said tray at said predetermined level for a sufficient period to start freezing an upper portion of said water from said top surface downwardly into clear ice, heating means maintaining a bottom portion of said water in a liquid state adjacent said bottom tray wall, and water fill means for refilling said tray with water to said predetermined level when the upper clear ice portion is removed from said tray, said fill means including a reservoir adapted to contain water therein in a liquid state at said predetermined level and means for maintaining water in said reservoir at said predetermined level, said reservoir being on the outside of said insulated cabinet wall substantially in the same horizontal plane as said tray, and conduit means interconnecting said reservoir and said tray from connections with said reservoir and tray below said predetermined level to place said reservoir in liquid flow communication with the bottom portion of water in the tray whereby water is supplied from said reservoir to said tray through said conduit means until the water level in said tray and reservoir is common at said predetermined level.
 13. The combination of claim 12 wherein the connection of said conduit means with said tray is in heat transfer relationship with said heating means whereby water in the conduit means on the inside of said insulated cabinet wall remains in a liquid state.
 14. The combination of claim 12 wherein the heating means and the connection of said conduit means with said tray are foamed in place by insulation on the outside of said tray walls. 